1. Field of the Invention
The invention relates to transportable locks, and more specifically the invention relates to padlocks where the lock mechanism of the padlock may freeze and prevent unlocking and opening the lock when used in cold and humid environments.
2. Background of the Invention
Conventional locks, including padlocks, are in widespread use for securing articles and doors. Padlocks often comprise a moveable U-shaped hasp or shackle that emanates from and inserts into the lock body and engages a lock assembly within the lock body to secure the shackle in a closed position. The lock assembly is most often a keyed lock or a combination lock. Often these locks are used outdoors or are exposed to conditions such as high-moisture-content air and freezing temperatures. For example, in the self-storage facilities industry many outdoor-accessible storage lockers are secured with renter-owned padlocks. In these situations, padlocks exposed to adverse weather are often used without any protective means employed to prevent freezing. Freezing weather frequently leads to a problem where a key will not turn a frozen lock mechanism in the padlock, leading to the result of the frozen locks being cut off and destroyed because they cannot be opened while frozen.
Several methods are known in prior art for preventing the freezing of the lock by protecting it from the contamination of moisture and other elements. Other methods exist that are employed for thawing the lock to enable the lock to be opened.
One general approach to the problem of the frozen lock is to protect the lock from the elements, and there are a variety of protective means disclosed in prior art. One method is to completely encase the padlock in a protective material, such as flexible plastic, rubber, or a rigid material such as metal. One example is U.S. Pat. No. 6,467,316, which discloses a rigid protective sleeve around a padlock. Another example is U.S. Pat. No. 6,192,721, which discloses a flexible pouch in which the padlock is encased. There are also several disclosures of seals which fit over the keyhole or around the shackle holes, such as in U.S. Pat. No. 6,813,914. All of these approaches may help prevent a frozen lock by keeping moisture out of the lock, but they do not help free a lock which becomes frozen in spite of the protective means. Further, most of these devices require they be separately acquired and applied to a lock. Lock users who do not take these precautionary measures find the unprotected lock may become frozen and therefore, must be destroyed if prompt opening is required.
Another approach to the frozen lock problem is to design the lock itself by having a protective means incorporated in the design and manufacture of the lock device. One example is in U.S. Pat. No. 6,860,127, which discloses a weather-resistant lock apparatus. Locks designed to be weather-resistant may help prevent a frozen lock, but suffer the same problem as lock protectors in that the features do not help free a lock which becomes frozen in spite of the protective design. Users often don't anticipate sudden changes in the weather and are left with the same problem that conventional pad locks suffer from in freezing conditions.
Still yet another approach to the frozen lock problem is a device for thawing the frozen lock. One approach in the prior art to thawing locks is to heat an apparatus which is inserted into the key slot to warm the locking mechanism from its key cavity. For example, U.S. Pat. No. 4,732,562 describes a device which heats a metal rod which is then inserted into a keyed lock to thaw the locking mechanism. This invention requires that the separate heating device be available when encountering a frozen lock. This can be burdensome, since often large numbers of locks are present and used infrequently by a large number of people, but only a few of them will be frozen at any time they need to be opened. Having such a device available to a large number of people for infrequent use is difficult to arrange. Another suggested approach is to heat the key that is used in each individual lock. U.S. Pat. No. 4,304,548 describes a modified cigarette lighter which heats an attached key before inserting the key in its lock, so that the key can heat the inside of the lock mechanism that is frozen. This invention also requires that the device be available when encountering a frozen lock, and also can pose a safety hazard if the key is overheated.
Other approaches exist for thawing frozen locks, such as using anti-freeze sprays or splashing warm water on the frozen lock. These techniques require the availability and use of separate components which may not be available to a lock user when encountering a frozen lock, as may be the case with other techniques. The addition of fluids to a frozen lock may even provide an increased capacity to freeze by introducing moisture to an already-frozen lock. Both of these traits make these approaches undesirable or ineffective for the problem.
Further, there are suggestions to use warm hands or blow warm breath onto the lock. A very cold lock touching bare skin, however, may freeze the skin on the hands of the person trying to thaw the lock. And breathing or blowing hot air on a frozen lock requires a long time and great amount of effort if the lock is very cold, making it a difficult and time-consuming approach. Breathing may also introduce moisture to the lock that may make the lock's capacity to freeze increase, rather than make the lock thaw.
As noted, the previous approaches to the frozen lock suffer several shortcomings. First, the use of an external protective means on a lock device may keep some moisture and contamination out, but cannot prevent freezing, and these approaches are not helpful once a lock is already frozen. Second, prior art methods for thawing the lock either require special equipment that can be misplaced or may not be available when needed, or may not be applicable to padlocks such as those used in cold temperature environments. Third, specially-designed weather-resistant locks are complex and tend to be expensive to manufacture.
Thus, based on the prior art and known designs, there is a need for a padlock device which does not require external protective parts that can be lost or misplaced. There is also a need to have a means of warming an internal region within a padlock device sufficiently such that frozen moveable parts in and around a lock housing may become thawed for normal operational use. Furthermore, there is a need for such a padlock device that is capable of being manufactured and maintained inexpensively and capable of effectively providing power needed for such a proposed warming function.